Hard to tell what the problem with 'reading more' etc. could be, since the English I learn is as a foreign language, so the methods used are probably different. But our teachers tell us the same -- reading more helps tons... only depending on what the student's problem is, because 'reading more' has never helped me to explain what makes modality X epistemic, unless it was a grammar book, that is.
What kind of questions did you have to answer during your test? Are these grammar-related questions? Vocabulary to find? Short texts to analyze and comment? Depending on this, what you have to 'read more' will be quite different, and you won't be able to use it the same way every time. Nor will it necessary help as much as it could in another context.
As for keeping weight and marks separated, I must admit I don't know, since I don't do it myself... although I do it the other way (every morning I 'convince' myself that if I eat healthy foods, my brain will work better and I'll do better at school. XD Which is true, so it does help). Do you stress-eat while doing your homework, perhaps? In that case, would it be possible for you to go study to a place where food is forbidden, or at least not easily available? (Like public libraries here, where we're not allowed to bring food, coffee etc.)
The flash cards idea sounds pretty good. It is useful all the same, and you can't grab food when your hands are full of them, I suppose.
